Automated bolus chase peripheral MR angiography: Initial practical experiences and future directions of this work-in-progress

Purpose: To evaluate how cine phase-contrast (PC) flow data correlate with the severity of peripheral vascular disease (PVD). Materials and Methods:Flow waveforms were obtained in 48 patients proximal and distal to superficial femoral artery (SFA) disease using the 2D cine PC technique with velocity encoding (venc) ϭ 100 cm/second. Flow data were correlated with SFA disease severity and compared with data from nine healthy volunteers.Results: Of 96 arterial segments in 48 patients, 26 were patent or only mildly stenotic, 35 had moderate-to-severe stenosis, and 35 were occluded. The flow patterns tended to become lowresistant below severe stenoses or occlusion. The mean peak flow velocity above/below SFA lesions was significantly higher in patients with severe disease (1.9 Ϯ 1.0, P ϭ 0.01) or occlusion (2.0 Ϯ 1.0, P ϭ 0.003) compared to normal volunteers (1.4 Ϯ 0.6). The delay in peak velocity below the lesions showed a significant positive correlation with lesion severity (r ϭ 0.65, P Ͻ 0.001). The mean flow volume ratio above/below SFA lesions was greater in patients with occluded vessels compared to normal volunteers (3.9 and 2.3 respectively; P ϭ 0.04). Conclusion:Cine PC flow waveform changes across atherosclerotic lesions correlate with disease severity. This may help determine which lesions are hemodynamically significant.

Section: Methodsmentioning

confidence: 99%

Superficial femoral artery occlusive disease severity correlates with MR cine phase‐contrast flow measurements

Mohajer

Zhang

Gurell

et al. 2006

“…Each patient received 35 mL of gadolinium DTPA (Magnevist, Schering, Berlin, Germany) administered at a rate of 1.8 mL/second for the first 15 mL and 0.6 mL/second for the remaining 20 mL (total injection duration: 42 seconds), followed by a saline flush of 20 mL at 0.6 mL/second. The injection rate was increased compared to protocols described in the literature (1–4) because we felt that use of the dedicated coil alone would not entirely compensate for the loss in SNR due to shorter aortoiliac and thigh acquisition times and the use of halfscan (i.e., half number of excitations [NEX] or half Fourier imaging in the phase encoding direction [75% K‐space filling]). Using the three‐station coil we attempted to image the pedal arch whenever this was requested by the referring clinician ( N = 12), and table occupancy was approximately the same as with the old protocol (∼20 minutes), but reconstruction and postprocessing required about five minutes longer per patient due to the increased number of phased array reconstructions.…”

Section: Methodsmentioning

confidence: 99%

“…AS AN ALTERNATIVE to intra‐arterial digital subtraction angiography (IA‐DSA) for the evaluation of peripheral arterial occlusive disease (PAOD), excellent diagnostic results have been reported using three dimensional contrast‐enhanced magnetic resonance angiography (CE‐MRA) (1–5). Although different MR approaches to peripheral arterial imaging have been described, the most often used technique at present is the acquisition of three overlapping coronal three‐dimensional gradient recalled echo scans during intravenous injection of a single bolus of 0.2–0.3 mmol/kg extracellular gadolinium chelate contrast medium.…”

mentioning

confidence: 99%

Use of a three‐station phased array coil to improve peripheral contrast‐enhanced magnetic resonance angiography

Leiner

Nijenhuis

Maki

et al. 2004

Purpose:To explore the imaging capabilities of a new commercially available, three-station, 129-cm long, 12-element phased array coil for contrast-enhanced magnetic resonance angiography (CE-MRA) in patients with symptomatic peripheral arterial occlusive disease. Materials and Methods:Nineteen patients, referred for peripheral CE-MRA, were evaluated using the new threestation coil. For each station four coil elements (two anterior and two posterior to the patient) were used. The expected improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were used to improve spatial resolution and increase anatomic coverage for the distal two stations compared to our previous protocol. Images obtained in the 19 patients imaged with the new coil were compared to those of the last 19 patients scanned without the use of the new coil. Differences in image quality before vs. after the availability of the new coil were compared in terms of SNR and CNR, subjective interpretability score (SIS), degree of venous enhancement, and anatomic coverage. Images were interpreted by two experienced observers, blinded for imaging technique and each other's results. ). SNR and CNR were significantly higher only in the aortoiliac station using the three-station coil (both: P Ͻ 0.001). There were no significant differences in SIS for the aortoiliac and thigh stations (aortoiliac station: observer 1: P ϭ 0.16, observer 2: P ϭ 0.19; thigh station: both observers: P ϭ 0.27). Images acquired with the new coil had significantly higher SIS for the leg station (both observers: P ϭ 0.004). There were no significant differences in venous enhancement between the two protocols for any of the stations (all P Ͼ 0.11). In 12/12 (100%) requested cases the entire pedal arch was depicted using the new coil, whereas this was not possible with the old protocol. Conclusion:The new three-station dedicated peripheral vascular coil allows for much higher resolution imaging in the thigh and leg stations with greater anatomic coverage and substantially improves peripheral MRA quality of the lower leg vasculature.

“…The proposed array is utilized for peripheral magnetic resonance angiography (MRA). MRA has been revolutionized by the bolus chase technique in which a single bolus injection is imaged multiple times as it travels down the peripheral arteries (3, 4). This technique overcomes the normal FOV limitations of MR scanning, but presents significant design challenges for receiver coils.…”

mentioning

confidence: 99%

“…This technique overcomes the normal FOV limitations of MR scanning, but presents significant design challenges for receiver coils. Historically, bolus chase experiments employed the body coil for signal reception (3–7). While this approach simplified image data acquisition, image quality was limited by poor SNR achieved by the large body coil.…”

mentioning

confidence: 99%

Design of a birdcage array for lower extremity angiography

Brown

Prince

Ersoy

et al. 2007

Purpose:To investigate the application of a coil array consisting of multiple birdcages for bolus chase magnetic resonance angiography (MRA) of the lower extremities. Materials and Methods:The prototype consisted of four birdcage coils; two adjacent birdcages for thigh imaging, and two for calf imaging. Decoupling between adjacent coils was achieved using shared capacitors. Bench measurements and MR images were used to evaluate the decoupling scheme. Image signal-to-noise ratios (SNR) were compared between the birdcage array and four commercially available coils. Contrast-enhanced imaging experiments were performed on 10 volunteers and parallel imaging was simulated. This study was approved by the local institutional review board and written informed consent was obtained from each volunteer. Results:Capacitive decoupling resulted in a reduction in signal leakage. The calf birdcages provided an 84% SNR improvement over a four element array, while the thigh birdcages provided a 53% improvement. Angiographic images illustrated the utility of the coil for peripheral MRA. Parallel imaging was demonstrated with a two-fold reduction factor. Conclusion:Birdcage coils were demonstrated to be valuable for lower extremity imaging due to their homogenous sensitivity, good SNR, and cylindrical geometry. Coupling was controlled using shared capacitors that allowed a single birdcage to encompass each leg individually, providing a novel approach to signal reception for peripheral imaging.